The stationary battery: lifespan and internal resistance

Batteries are essential and highly necessary components in energy systems for telecommunications. Therefore, we present to you the following information about stationary batteries and their types.

Before we proceed, it’s a great idea for you to read our post Batteries and their fundamentals to make the most out of this content.

What are stationary batteries?

This is a type of battery designed to provide power to stationary systems; they are a highly reliable source.

They are characterized by their long-term durability and large storage capacity, allowing them to provide energy in a very stable manner. This is particularly useful for high-power loads over extended periods, as they can withstand deep discharge cycles without damage.

They are used in industries, telecommunications, and critical systems where an uninterrupted and reliable power source and backup are required.

These batteries, depending on their capacity, have a specific number of cells at 2 Vdc. Therefore, these batteries can be 2, 6, and 12 Vdc, which are the voltage levels currently standardized worldwide.

Now, depending on the voltage of the power system they are backing up, a certain number of these batteries will be required. These batteries need to be connected in series (Wikipedia).

This configuration is known as a battery bank. Depending on factors such as space, power requirements, etc., more than one bank might be necessary.

In our Sizing and design of DC power systems for telecommunications course you will find more detailed information on this topic.

Characteristics of stationary batteries

While there are various types of stationary batteries, there are certain common characteristics shared among all of them. You should consider these when selecting them. We will now discuss these characteristics.

Battery lifespan

Unlike conventional equipment, the lifespan of stationary batteries depends on their usage. It’s determined by the number of discharge-recharge cycles as well as their depth.

In this regard, if the discharges are very deep, the battery’s lifespan decreases. The maximum allowable depth of discharge for a battery without causing significant damage is around 80% of its nominal capacity.

In the image below, you can observe how the depth of discharges affects the number of discharge cycles a battery can endure.

In addition to depth of discharge, which is the most important factor, there are other elements that influence the lifespan of batteries. These factors also have a significant impact on battery performance. Here are some of them:

• Frequency of discharge-recharge cycles
• Battery capacity vs demand
• Constant battery charge level
• Recharging system
• Temperature
• Battery composition and design
• Maintenance, if needed
• Technology

These factors collectively contribute to the overall performance and longevity of stationary batteries.

Internal resistance of batteries

This parameter represents the cumulative effect of this characteristic from the various components of the battery. These components include electrodes, terminals, electrolyte, and supports, along with a virtual resistance value that changes based on the charge level.

The resistance values, depending on the battery’s state, are provided by the manufacturer. Measurement is performed using a specialized device known as a battery internal resistance or conductance meter.

This terminology varies depending on how the equipment measures this variable. It’s important to note that conductance is the reciprocal of resistance and is expressed in Siemens. Mathematically, it’s determined as follows:

If the manufacturer provides values in Ohms and the equipment measures in Siemens, you just need to apply the equation we provide.

At energydcac, you will find highly relevant content related to this equipment and DC power systems in general, as well as various components. Don’t miss out on reading them!

Similarly, we recommend our Sizing and design of dc power systems for telecommunications course. You can access its content here.

Image sources

• emeisa.mx
• energydcac.com